I have a Tagaki T-H3-DV-N (Indoor) tankless hot water heater. It has a condensation drip spout, and drips about 1 gallon of water per day. Is this excessive or normal?

Edit: I've spoken to the manufacturer who have zero specs on this. Tagaki support wouldn't even say that a gallon a minute was excessive. They were not helpful. The 3rd party seller (a radiant floor company) said a gallon a day seems high, but might not be depending on usage.

I'm currently running a longer test to get a better average number of the flow rate. Will report back.

Edit 2: Longer test on a fairly cold week gives ~0.57 gallon/day. Seems reasonable according to the manufacturer and seller.


That seems high to me, but it's mostly dependent on your gas supply moisture level (they have tolerance for moisture inside your gas line) and the humidity in your combustion air supply. Do you live in a moist or high-humidity area? Has it changed recently, i.e. more water being discharged all of a sudden?

  • New system so I don't have a baseline. House (intake) moisture is ~50 +-10 %. – mankoff Nov 27 '15 at 17:14
  • 50% moisture is pretty high for intake air at this time of year anyplace you need gas heat. should be more around 25-40%. you haven't recently added or moved a dryer vent or exhaust fan to near to your intake port have you? was this ODWH (on-demand water heater) installed recently, and if so, DIY or pro installation? the reason I ask is that if you have an incorrectly sloped, too long run or partially blocked run of exhaust pipe, you could be getting incomplete venting of your exhaust gases, thus leading to increased humidity in the house and causing the increased condensate. – personal privacy advocate Nov 28 '15 at 18:03
  • I would make sure you have a functioning and current CO detector and keep an eye on it, or maybe just bite the bullet at get an HVAC tech in to have a look. its very difficult to say without looking at the system and installation, but it sounds like you definitely are getting too much humidity. – personal privacy advocate Nov 28 '15 at 18:03
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    Hi @personal. I live in central PA. It is 80% humidity all summer outside, and I can keep it at 60% inside by running dehumidifiers. My little humidistat says the past 24 hours have been 46-56%, which is just what it is in the house. Always. Nothing new here. On demand hot water heater installed by pro about 3 weeks ago. Intake is inside. Exhaust run is 4" PVC and about 10 feet with no curves. I'll check with HVAC pro. – mankoff Nov 28 '15 at 20:31
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    Longer test: ~0.5 gallon/day. Seems reasonable. – mankoff Dec 6 '15 at 16:46

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